Stereoscopic systems provide a viewer with a three-dimensional representation of a scene (or an object), using two or more, two-dimensional representations of the scene. The two-dimensional representations of the scene are taken from slightly different angles.
The goal of stereoscopic systems is to produce one or more binocular views of a scene to the viewer. A full-parallax view accurately simulates depth perception irrespective of the viewer""s motion, as it would exist when the viewer observes a real scene.
Stereoscopic systems include autostereoscopic systems and non-autostereoscopic systems. Non-autostereoscopic systems require a viewer to use a device, such as viewing glasses, to observe the three-dimensional view, while the three-dimensional effect of autostereoscopic systems may be observed by viewing the system directly.
Early stereoscopic devices used prismatic, total internal reflection (TIR) to simultaneously present two views of a scene, such as the Swan Cube. Prismatic TIR allowed the views to be presented to the viewer such that each of the viewer""s eyes was presented one of the two images, thus creating a perception of depth. Prismatic devices simulate depth perception for only a single viewing angle.
After the introduction of transparent plastic optics, autostereoscopic devices using one-dimensional arrays of cylindrical lenses (known as lenticular lenses) were created. A lenticular lens array has an associated array of composite strip images. Each lenticular lens presents the viewer a selected portion of its strip image such that the combined presentation of all of the lenticular lenses presents a three-dimensional view of the scene.
Devices using lenticular lenses have several shortcomings. First, because the lenticular lenses are cylindrical (i.e., they have optical power in a single dimension), they produce parallax only on a horizontal viewing axis. If the viewer""s viewing angle departs from the horizontal viewing axis, the three-dimensional representation ceases to exist. Second, the lenticular lenses are highly astigmatic, and therefore, the viewer cannot bring the three-dimensional representation fully into focus. Third, if the two-dimensional images require illumination through the lenticular arrays (i.e., the images are not self-radiant, or the images are not printed on a transparent or translucent material that is capable of backlighting), the three-dimensional presentation will have uneven radiance resulting from uneven distribution within the array.
Another autostereoscopic system uses an array of spherical (or aspherical) lenses. Spherical lens array systems have an associated two-dimensional array of microimages. Each microimage is a two-dimensional view of a scene, captured from a slightly different angle. Unlike lenticular lenses, spherical lenses have optical power in two dimensions, thus allowing the viewer to maintain a three-dimensional representation of a scene despite departing from the horizontal viewing axis.
Each spherical lens presents the viewer a selected portion of a corresponding microimage such that the combined presentation of all of the spherical lenses presents a three-dimensional view of a scene. Ideally, each lens system of the lens array corresponds to a single microimage, such that when a viewer views the microimages through the lens array, each lens system transmits a single color or tone, from a selected portion of a single, corresponding microimage.
The shortcomings of spherical arrays have included that lenses in a lens arrays have excessive aberrations and a tendency to transmit light from multiple microimages. Both of these shortcomings have resulted in reduced image quality.
An additional advantage of spherical (or aspherical) arrays of lenses is there ability to capture arrays of microimages for use with three-dimensional viewing systems. The process of capturing arrays of microimages is known as integral imaging. An image captured by a spherical lens array is initially pseudoscopic, but may be made orthoscopic by reproduction of a captured image using a second array.
A difficulty encountered in capturing and reproducing images is optical crosstalk between lens systems of the array. Crosstalk causes overlap of adjacent images, resulting in degradation of the microimages. Solutions to crosstalk have ranged from modifications of the scene when creating the microimages, to optomechanical modifications of the lens arrays. Optomechanical modifications of the lens arrays have included baffles that limit the field of the lens systems comprising a lens array. The baffled lens systems are said to be field-limited. And a field-limited system whose field does not overlap the field of adjacent lens systems is said to be xe2x80x9cisolated.xe2x80x9d Solutions to crosstalk have been costly to implement.
An aspect of lens systems of the present invention is a high acuity lens system comprising three optical boundaries having optical power. The lens system comprises a first boundary having a radius of curvature R, a second boundary located substantially a distance R from the first surface, and a third surface located at least 0.05 R from the second boundary.
Another aspect of lens systems of the present invention is a lens array having a lens system that is xe2x80x9coptically field-limited.xe2x80x9d An optically field-limited system is a system wherein the edges of the field of the system are determined by the optical properties of lens material of the system. Accordingly, in the present invention, light within the field of a lens is substantially transmitted by the lens, and light at greater field angles than the edges of the field is substantially reflected by a surface of the lens system, using total internal reflection.